Apparatus for making an absorbent composite product

ABSTRACT

A multi-layer absorbent product in a preferred embodiment includes a fibrous nonwoven top sheet, a fibrous nonwoven absorbent core layer, and a fibrous nonwoven substantially water-impervious back sheet. Each component layer or sheet is manufactured at a fiberizing station (i.e., melt spinning) and laminated together at a combining station. The preferred melt spinning apparatus is spunbond for the top sheet, meltblowing for the core layer, and a combination of spunbond and meltblowing for the bottom sheet.

FIELD OF THE INVENTION

The invention generally relates to equipment and processes for in-linemanufacture of absorbent products. The equipment and the process utilizesynthetic resins, such as thermoplastics, for the in-line manufacture ofa multi-layer absorbent product. The invention also relates to acomposite absorbent product comprising at least an impervious nonwovenbottom sheet, an absorbent nonwoven core, and a nonwoven top sheet.

BACKGROUND OF THE INVENTION

The equipment used for in-line manufacture of absorbent products, suchas diapers, sanitary napkins, adult incontinent pads and the like, isgenerally referred to as converter equipment and the process isgenerally referred to as converting. The converter equipment processesseparate rolls of stock material into the composite absorbent product.The converter equipment generally comprises stations for manufacturingthe composite absorbent product as follows:

(a) An absorbent core forming station comprising a hammermill is fed bypulp roll stock, such as cellulosic material with or withoutsuperabsorbent. The hammermill fiberizes the pulp, and a drum form orflat screen then forms the fiberized pulp. Alternatively, the absorbentcore material can be supplied in roll form.

(b) A top sheet station supplies a top sheet or coverstock layercomprising a nonwoven, such as spunbond polypropylene. The top sheet isunwound from a roll and applied to the core layer.

(c) A bottom sheet station for supplying a liquid-impervious backsheet,such as polyethylene film, which is applied to the top sheet/corecombination.

The absorbent product is a composite comprising a top sheet or coverstock, an intermediate core layer of absorbent material, and a bottomsheet or back sheet of impervious film. Most converter equipmentincludes devices for adding a variety of options, such as elasticwaistbands and legbands, tab applicators, frontal tape applicators,transfer layers, and the like.

A characteristic common to all converter equipment and processes is thatthey use only roll stock to form the layers of the absorbent product.The roll stocks are separately manufactured into rolls, typically offsite, and then transported to the site of use. These rolls are processedby the converter equipment to form multiple layer absorbent products.

Converter equipment typically comprises a large complex laminatingmachine which requires significant horizontal and vertical plant space.The complex equipment requires constant attention and fine tuning. Also,converter equipment generally produces a one-line output so the unitoutput is directly proportional to the line speed. Accordingly, theconverter equipment must operate at extremely high speed, such as atline speeds of 700 to 1200 ft./min., to be economical.

As the converter equipment handles only preformed roll stock, it has aserious operational disadvantage. That is, once the multiple rolls areinstalled, the composition, properties or dimensions of the roll stockscannot be changed. In order to produce two different types of absorbentproducts, or absorbent products with different properties, the convertermust be shut down and a new roll or rolls substituted for the existingroll or rolls. For these reasons, it would be desirable to eliminate oneor, preferably, more of the conventional roll stocks and form differentlayers of an absorbent composite product in-line.

SUMMARY OF THE INVENTION

The method and apparatus of the present invention most preferablyinvolve fiberizing or melt spinning a synthetic resin, such asthermoplastic, at three separate stations. These three stations comprisea top sheet forming station, a core layer forming station, and a bottomsheet forming station.

The top sheet forming station includes at least one fiberizing die, suchas a spunbond die, to form a nonwoven top sheet which is deliveredin-line to a combining station. The bottom sheet forming stationincludes at least one spunbond die and, preferably, one or moreadditional meltblowing dies to form a water-impervious composite bottomsheet. The bottom sheet is preferably conveyed directly (in-line) to thecore layer forming station where one or more meltblowing dies deposit ameltblown layer or a plurality of meltblown sublayers onto the bottomsheet to form a bottom sheet/core layer composite. The bottom sheet/corelayer composite is conveyed in-line to the combining station where it islaminated with the top sheet to form an absorbent composite inaccordance with the invention. In particular, the absorbent composite ofthis invention preferably comprises:

(a) an inner top sheet of strong, fluid-permeable nonwoven;

(b) a middle absorbent core layer of a nonwoven composed of hydrophilicmicrosized fibers, with preferably a sublayer of a coarser nonwoven incontact with the top sheet to aid in distributing liquid permeating thetop sheet; and

(c) a substantially fluid-impermeable back sheet of a strong nonwovenfor containing the core layer and retaining fluid collected or absorbedtherein.

Variations in the invention include using fiberizing dies at twostations, such as the top sheet and core layer forming stations, withroll stock used at the third station. Other variations of fiberizingdies and roll stock may be used as well. Also, the three layers may beaffixed to one another, whether using fiberizing dies or roll stock, invarious orders not withstanding that a preferred order of manufacture isspecifically described herein.

The absorbent composite may be made an overall width transverse to themachine direction equal to multiple widths of each individual absorbentproduct. In such an embodiment, the composite width is slitlongitudinally along the machine direction to form a plurality of slits,each slit being equal to the width of one absorbent product. The slitsare then cut at longitudinal intervals to form individual absorbentproducts.

As described herein, the present invention contemplates severalembodiments. Advantages and distinguishing features of some or allembodiments may be summarized as follows:

(1) The absorbent composite comprises three or more layers or sheets ofmicrosized fibers.

(2) Fiberizing or melt spinning of each component sheet or layer of thecomposite avoids the need for a converter. Thermoplastic resin isprocessed on site to form the compound sheets or layers and conveyedin-line to the combining station.

(3) The in-line manufacture of the component sheets or layers permitsthe rapid and easy change of materials (e.g., polymer grade), propertiesof the sheets or layers, and operating conditions.

(4) The manufacture of the large widths equal to several widths ofindividual absorbent products permits the line to operate at only afraction of the speed of converters in achieving the same unit output.

Additional objectives, advantages and features of the invention willbecome more readily apparent to those of ordinary skill in the art uponreview of the following detailed description of the preferredembodiments, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation schematic view of a line for fiberizing andlaminating three nonwoven sheets or layers to form an absorbentcomposite.

FIG. 2 is a side elevational of a line illustrating three extrudersarranged in line for preparing a composite comprising three differenttypes of nonwoven sheets or layers.

FIG. 3 is a cross-sectional view illustrating the three component layersof the disposable laminate.

FIG. 4 is an enlarged front view of a meltspinning assembly shown ineach of the extruders of FIG. 2.

FIG. 5 is an enlarged view of a meltblowing insert useable in theassembly of FIG. 4.

FIG. 6 is an enlarged view of a spunbond die insert useable in theassembly of FIG. 4.

FIG. 7 is a top plan view, shown in schematic, illustrating a line formanufacturing disposable articles by longitudinally slitting the lineoutput to form a plurality of parallel strips that are cross cut intoindividual articles.

FIG. 8 is a schematic view similar to FIG. 1 illustrating anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As mentioned above, the preparation of a composite absorbent comprisesat least three main layers: (a) a top sheet, (b) an absorbent corelayer, and (c) a substantially fluid-impervious bottom sheet. At leasttwo of the layers are nonwovens prepared by extruding a thermoplasticpolymer to form a nonwoven layer which is combined in-line with theother two layers. The term “in-line,” as used herein, means thecontinuous laminating of an extruded nonwoven layer with another layerwithout the usual intermediate step of forming rolls of the nonwovenlayer. It is preferred that at least two of the layers be formed byin-line extrusions. In the most preferred embodiment, all three layersare formed by in-line extrusion.

FIG. 1 illustrates the most preferred embodiment as comprising threestations: a top sheet forming station 201, a bottom sheet formingstation 202, and a core layer forming station 203. Nonwovens are formedat each station. The order of stations shown and described herein ispreferred, but the order of operation may be changed as well.

The term “nonwoven” refers to a sheet, web or batt of directionally orrandomly oriented fibers, made by bonding or entangling the fibersthrough mechanical, thermal, or chemical means. Nonwoven fabrics excludepaper and products which are woven, knitted, tufted, or felted by wetmilling. The fibers are preferably man-made synthetics.

Although nonwovens may be made by a number of processes, the mostpopular processes—and those preferred for use in the presentinvention—are meltblowing and spunbond processes, both of which involvemelt spinning of thermoplastic material. Meltblowing is a process forthe manufacture of a nonwoven fabric wherein a molten thermoplastic isextruded from a die tip to form a row of fibers. The fibers exiting thedie tip are contacted with converging sheets or jets of hot air tostretch or draw the fibers down to microsize diameter. The fibers arethen deposited onto a collector in a random manner and form a nonwovenfabric.

The spunbond process involves the extrusion of continuous filamentsthrough a spinneret. The extruded filaments are maintained apart and thedesired orientation of the filaments is achieved by rotating thespinneret, by electrical charges, by controlled air streams, or by thespeed of the collector. The filaments are collected on the collector andbonded by passing the layer of filaments through compacting roll and/orhot roll calendaring.

Spunbonded webs generally have large average diameter (e.g., 12-100microns, typically 12-50 microns) which are heavier and stiffer thanmeltblown fibers. The meltblown fibers are generally smaller in averagediameter (0.5 to 15 microns) than the spunbond fibers, but themeltblowing die assemblies can be operated to make much larger fibers.

A paper presented at “Fiber Producer Conference 1983,” in Greenville,S.C., entitled “Nonwoven Fabrics: Spunbonded and Meltblown Processes”describes the two processes in detail. The disclosure of this paper areincorporated herein by reference. It should be noted that the terms“fibers” and “filaments” when used in connection with nonwovens andprocesses for manufacturing nonwovens are interchangeable.

The Absorbent Product

The absorbent product of the present invention comprises at least threeseparate main layers that contribute separate properties and functionsto the composite. As shown in FIG. 3, the absorbent product 200comprises three main layers:

a top sheet 235,

a core layer 237, and

a bottom sheet 238.

The top sheet 235, sometimes referred to as cover sheet, covers the corelayer 237 and contacts the wearer. It accordingly must exhibit comfortand be capable of transmitting fluid to the core layer 237. The topsheet preferably is made up of spunbound fabric, which exhibits aclothlike band and is fluid permeable. The fluid is generally a bodyfluid such as urine.

The core layer 237 is the absorbent layer and may comprise twosublayers, a thin acquisition and distribution layer 239 and a mainabsorbent layer 241. The core layer 237 preferably is made of ameltblown hydrophilic polymer which exhibits high absorbency. Thedifference between the distribution layer 239 and main absorbent layer241 is one of degree, the former being made of coarser fibers (at least5%, preferably 10%, and most preferably 25% coarser) than those of thelatter to promote liquid distribution from the top sheet 235 to layer241.

The bottom sheet 238, sometimes referred to as the back sheet, is asubstantially liquid impervious sheet. This sheet generally is athermoplastic film, but in accordance of a preferred embodiment of thepresent invention, is a combination of a spunbound layer and a meltblownlayer, as described in detail below.

Each of the sheets or layers 235, 237, and 238 may be composed of aplurality of sublayers to impart or enhance the desired propertiesthereto.

The three distinct layers of the composite absorbent thus performseparate and diverse functions. When using conventional converters inaccordance with the prior art, each layer, in roll stock, must bepreselected, leaving no flexibility for altering the properties ordimensions of each selected layer. The in-line manufacture andlamination of layers in accordance with the present invention offersmany significant advantages over the converter approach, but oneadvantage stands out; and that is the exceptional flexibility—within thelimits of the equipment employed.

The Process and Apparatus

The preferred process and apparatus of the present invention will bedescribed with reference to FIG. 1, it being understood that otherembodiments, such as that depicted in FIG. 8, are also contemplated.

With reference to FIG. 1, the in-line manufacture of an absorbentcomposite 200 comprises three main fiberizing stations: a top sheetforming station 201, a back sheet forming station 202, and a coreforming station 203. As described in detail later, each station mayinclude more than one fiberizing die for applying more than one layer ateach station. (The term “fiberizing,” as used herein, means theextrusion of a thermoplastic into filaments of fibers.)

Top Sheet Forming Station

The top sheet forming station 201 includes a die assembly 207 forextruding a plurality of synthetic fibers 204. The fibers are collectedinto a web 206 which, after further processing, is delivered, in anin-line fashion, to a layer combining station 205. Note that web 206corresponds to top sheet 235, shown in FIG. 3. The top sheet 235 is thelayer of the absorbent product that contacts the wearer, must be liquidpermeable, and must possess a certain amount of integrity for assemblageand retention of the core layer. For this reason, the preferred topsheet 235 is a spunbonded web manufactured by a spunbond die. Althoughmost spunbound dies may be used, the preferred top sheet forming stationincludes a die assembly 207 shown in FIG. 1 and described in more detailbelow.

A synthetic thermoplastic resin such as polypropylene is processedthrough the die assembly 207 into filaments 204 which are collected on amoving conveyor 208 (e.g., screen) as a loose web. The web is passedthrough a calendar 210 to bond the filaments together forming web 206.The web 206 is conveyed along rollers 212 to the combining station 205.

Any of the thermoplastic resins used in spunbond dies may be used toform layer 206. Polymers are copolymers of propylene and ethylene arepreferred polymers with polypropylene being the most preferred.

Bottom Sheet Forming Station (202)

In order to provide the properties and strengths necessary for thebottom sheet 238 (i.e., back sheet), station 202 is preferably acombination of a spunbond die assembly 214 and at least one meltblowingdie assembly. Preferably, station 202 uses two meltblowing dieassemblies 216A and 216B. As schematically illustrated in FIG. 1, thespunbond die assembly 214 processes a thermoplastic resin such aspolypropylene into filaments 218 which are collected as a web 220 onto amoving conveyor (e.g., a screen), described in more detail below withreference to FIG. 2. The web 220 is then passed through a calendar 224to bond the filaments into a strong integrated web 226. Note that web226 corresponds to backsheet layer 238 shown in FIG. 3. Since the backsheet 238 must be substantially liquid impermeable, the nonwoven web 226should be treated to reduce its permeability. The terms “liquidimpervious” and “liquid impermeable” are used interchangeably herein,meaning an aqueous liquid will not pass therethrough under conditionsfor use. This can be accomplished by spraying a sealant (e.g., anadhesive) onto a surface of the web 226, but preferably is achieved bymeltblowing one or more layers of thermoplastic fibers onto the surfaceof web 226 by meltblowing die assemblies 216A and 216B.

As web 226 is conveyed under die assembly 216A by moving conveyor 228,or screen, meltblown fibers 230 are deposited thereon formingspunbond/meltblown composite 232. Continuous conveyance brings thetwo-layer composite 232 under the second meltblowing die 216B, whereadditional meltblowing of thermoplastic fibers 234 are sprayed onto thetop surface of the spunbond/meltblown (SB/MB) composite 232 forming athree-layer SB/MB/MB composite 236.

The composite 236 is then passed through calendar 233 to thermobond thethree layers together. In lieu of the calendar, adhesive may be used tobond the three layers together. Note that in this preferred embodiment,the SB/MB/MB composition 236 corresponds to backsheet 238 shown in FIG.3.

The gradation of the fiber sizes in the back sheet results in asubstantially liquid impermeable layer. The small-sized meltblown fiberscombined with their strongly hydrophobic nature acts as a barrier forwater. Moreover, the spunbond outer (exposed) layer gives the product amatte finish, strength, and a soft flexible hand. The liquid-imperviousback sheet should be greater than 300 mm, as measured by RCST (raisingcolumn strike-through).

An important property of the back sheet 236 made at station 202 is thatit is liquid (e.g., water) impermeable but air permeable (i.e.,breathable). This not only provides comfort to the wearer, but has amanufacturing advantage. The air permeability permits meltblown layer orlayers to be deposited thereon at station 203. In the meltblown process,the air/fiber mixture is delivered to a perforated conveyor such as ascreen. The air passes the screen leaving the fibers accumulated in arandomly packed deposit on the screen. Back sheets such as film do notpossess air permeability and therefore are not readily adapted forreceiving meltblown fibers thereon.

Core Forming Station

The third fiberizing station 203 comprises one or more meltblown dieassemblies. In FIG. 1, three meltblowing die assemblies 240A, 240B, and240C are shown. The dies can be operated to (a) extrude identical fibersto form identical webs, (b) extrude different fibers using the same typeof resin, or (c) extrude different fibers using different types ofresin.

The back sheet 238 leaving station 202 is conveyed successively underthe meltblowing die assemblies 240A, 240B, and 240C to receive a buildupof webs thereon. The back sheet 236, which can be a single web or acomposite, is passed under the first die assembly 240A wherethermoplastic fibers 242 are deposited thereon forming a composite 244.Composite 244 is then passed successively under die assemblies 240B and240C where fibers 246 and 248 increase the thickness of the core layer,The final core layer made by station 203 comprises a stack-up of threesublayers. It is preferred that the web formed from fibers 248 oncoarser (larger average fiber diameter) than the webs formed from fibers242 and 246. The coarser fiber layer serves as a liquid acquisition anddistribution layer for liquid permeating the top sheet as describedbelow. The composite 250 exiting station 203 may be viewed as acomposite of a back sheet 236 and a core layer 237, each of which may bemade up of one or more sublayers as described above.

Combining Station

The top sheet 206 and core/bottom sheet composite 250 are broughttogether and passed through counter-rotating rollers 211 of thecombining station 205. An adhesive may be applied to one of theconfronting surfaces to add strength to the laminate.

The final product is a composite 200 (shown in FIG. 3) comprising a topsheet 235, a core layer 237, and a back sheet 238. As will be describedin more detail below, the composite 200 is further processed throughin-line stations to complete and package the absorbent products such asdiapers.

In-Line Fiberizing Die Assemblies

As noted above, the fiberizing die assemblies (e.g., meltblowing andspunbond dies) useable at the various stations according to the presentinvention can be any of a variety of commercially available designs. Thepreferred fiberizing die assemblies, however, are disclosed in FIG. 2and described in detail in U.S. patent application Ser. No. 09/033,833,the disclosure of which is incorporated herein by reference. FIG. 2illustrates the bottom sheet forming station 202 as comprising dieassemblies 214 and 216A and core forming station 203 as comprising dieassembly 240A in accordance with one embodiment of the invention. Notethat the other die assemblies, 216B of station 202 and die assemblies240B and 240C of station 203 (if used) can be identical respectively todie assemblies 216A and 240A described with reference to FIG. 2.

The fiberizing die assemblies 214, 216A, and 240A of the multi-stationline may include many of the same components. Accordingly, the samereference numerals will designate the corresponding components of eachdie assembly. For example, the extruder at each die assembly 214, 216Aor 240A, is designated by reference numeral 22.

Referring specifically to die assembly 214, this station comprises asupport structure which may be in the form of four vertical legs 11 (twoof which are shown in FIG. 2 and two being obscured) interconnected bycross beams 12. Each of the legs 11 are hollow and are concentricallymounted over internal legs 13 which are anchored to the floor. The legs11 and 13 may be of any cross section but are preferably square and aresized to permit telescopic movement therebetween. The means fortelescopically moving the outer legs 11 in relation to the inner legs 13may take a variety of forms including hydraulic rams. The preferredheight adjuster, however, is a conventional screw jack assembly 50located at the upper end of each leg 11. The jack assembly 50 comprisesa gear box driven by drive shaft which turns screw. Screw is threaded tobushing affixed to the upper end of leg 11. Turning the screw in onedirection raises the legs 11 and support structure 15. The supportstructure 15 and equipment mounted thereon is thus moveable verticallybetween an upper position (die assembly 214) and a lower position (dieassembly 216A).

A melt spinning assembly, shown generally as 16, is mounted on themoveable support structure 15 by air pipes which include a pair ofvertical air pipes 18 and a horizontal pipe section 19. There are twopairs of air pipes 18, one pair being mounted on each side of the meltspinning assembly 16. One pair is connected to opposite ends of air box20 (see FIG. 4) of the melt spinning assembly 16 as described below. Thehorizontal pipe 19 of each pair of pipes may be secured to cross beam12. Thus, the melt spinning assembly 16 is suspended on the moveablesupport structure 15. The term “melt spinning assembly” is used hereinin the generic sense for fiberization referring to both meltblowing andspunbond die assemblies. The melt spinning assembly 16 of die 214includes spunbond die insert 65 shown in FIG. 6.

An extruder 22 mounted on the moveable support structure compriseshopper 23, barrel 24, and polymer feed line 25. The polymer feed line 25delivers polymer melt to the melt spinning assembly 16 as described inmore detail below.

Positioned directly under the melt spinning assembly 16 and in alignmenttherewith are a pair of air quench ducts 26 and a filament drawingdevice 27. These two components, 26 and 27, are both supported on aplatform 28 in stacked relationship by brackets. The pair of ducts 26define a quench zone 45 therebetween. The drawing device 27 is alsoconstructed as a pair of conduits defining a filament drawing orstretching zone 46 therebetween. The vertical space between the quenchducts 26 and the drawing device 27 may include sheet metal housing 47and the vertical space between drawing device 27 and platform 28 mayinclude sheet metal housing 29. The platform 28 has an opening 32 formedtherein. The filaments 30 discharging from the melt spinning assembly 16descend through the quench zone 45, housing 47, draw zone 46, housing29, opening 32, and are deposited as filaments 218 onto conveyor 36. Thecomponents 26, 27, 47, and 48 may be mounted on a wheeled carriage sothat this assembly may be moved as a unit to the operating position ormoved at right angles to the conveyor 36 to an offline position.

The conveyor 36 may traverse in underlying relationship all threeassemblies 214, 216A, and 240A or, as illustrated in FIG. 2, may be insections 36 and 36A to accommodate calendar 224. The collectors 36 and36A are adapted to collect filaments from each die assembly. Theconveyors 36 and 36A are each perforated or a fine-mesh screen to permitthe passage of air therethrough. Vacuum means 25 positioned underconveyor 36 and 36A at each die assembly may be used to withdraw the airand debris.

Air is delivered to the quenching ducts 26 as shown schematically byarrows 34, and air is delivered to the filament drawing device 27 asshown by arrows 35.

The drawing device may be of any prior art construction including thosedescribed in U.S. Pat. Nos. 4,340,563 or 5,545,371, the disclosures ofwhich are incorporated herein by reference. The spunbond filaments arestretched in the drawing device and laid down on collector 36 as web 220which is passed through calendar 224 to form web 226.

The melt spinning assembly 16 shown in FIG. 4 comprises a die 51,positive displacement pump 52 such as a gear pump, motor 53, gear box54, and shaft 56. The polymer feed line 25 delivers polymer melt to thespinning assembly 16. Motor 53 drives pump 52 which receives the polymermelt and delivers the same at metered rates to the die 51 whichdistributes and discharges the melt through orifices as filaments 30.

Air connectors 57 and 58 mounted on each side of the die 51 connect tothe air lines 18 which deliver pressurized hot air to the die 51 in itsmeltblowing mode (FIG. 5). The gear pump 52, motor 53, and gear box 54may be similar to that described in U.S. Pat. No. 5,236,641, thedisclosure of which is incorporated herein by reference. The die 51comprises a die body 61 having a downwardly opening cavity 62 formed inits lower end. Die body 61 may be constructed in halves as illustratedin FIG. 4, wherein one half has an internal passage 67 connected to line25 for feeding the polymer melt to the inlet of pump 52. The cavity 62is defined by two elongate side walls 63 and top surface 64. Elongate,V-shaped grooves are formed on each side-wall 63, as illustrated. Thedie body 61 has longitudinally spaced passages for interconnecting airconnectors 57 with opposite sides of the cavity 62.

The die body 61 may have formed therein a conventional “coathanger”distribution passage for feeding a polymer melt to the die insertsdescribed below. Electrical heaters may be mounted in the die block 61for maintaining the temperature of the die body at the operating level.As mentioned previously, the air box 20 on each side of the die body 61is suspended between pipes 18. Each air box 20 defines an internalelongate square chamber which extends substantially the entire length ofthe die body 61 and is connected to the air connector 57 through plateby welded connections. The connector 57 may be a welded assembly ofplates which in combination define an internal air chamber and is boltedto each side of body 61 by bolts. Each connector 57 conducts air throughpassages 92 to the die inserts 65. The die insert assembly 65 which fitsinto and is mounted within cavity 62 may be in the form of a meltblowingdie (herein referred to as meltblowing die insert) shown in FIG. 5 ormay be in the form of a spunbond spinneret (herein referred to as aspunbond die insert) shown in FIG. 6.

Referring first to the embodiment using the meltblowing die insert 96,this assembly comprises a support member 98 and a die tip 99 mountedthereon. Members 98 and 99 are joined by a series of bolts (one shown as109). Member 98 has a top surface 101 which contacts surface 64 ofcavity 62, and has side walls 102 which fit in close conformity with theside walls 63 of cavity 62. Also formed in the support member 98 are apair of longitudinally extending V-shaped grooves 104. These groovesalign with the cavity grooves with the insert 96 mounted in cavity 62. Aplurality of air holes 103 extend vertically through the support member98. The inlet of each air passage 103 is aligned with the outlet 92 ofeach air passage formed in the die body 61. Also formed in the supportmember 98 is an elongate channel 106 that extends through thelongitudinal axis thereof. The inlet of channel 106 registers withchannel 72 of the die body with the meltblowing die insert 96 mounted incavity 62. An O-ring 107 surrounds the inlet 106.

The die tip assembly 99 comprises a die tip 107 and a pair of air plates108. The die tip 99 has a downwardly projecting triangular nosepiece 11defined by converging surfaces 112 and 113. Surfaces 112 and 113 meet atapex 114, and a plurality of orifices 116 are spaced longitudinallyalong the apex 114. A polymer flow channel 117 extends through the dietip 99 and has an inlet which is aligned with polymer flow passage 106of support member 98. The flow passage 117 pinches down to deliverpolymer to the orifices 116. The nosepiece 111 may be integrally formedin the die tip 99 as illustrated or it may be a separate piece bolted tothe body of the die tip 99.

Also formed in the die tip 99 are air passages 118 which register withair passages 103 of support member 98. The air plates 108 are mounted onthe die tip 99 by a plurality of bolts, one shown as 119. The air plates108 flank the nosepiece 111 and define a converging gap 121 betweenconfronting edges of the air plates 108 and surfaces 112 and 113. Eachair plate 108 defines with a confronting surface of the die tip atortuous air passage 124.

The meltblowing die tip insert 96 fits in close conformity in cavity 62of the die body 61. The polymer flow passages and air passages of theassemblies are respectively in fluid communication so that air flowsthrough the assembly and discharges as converging air sheets at the apex114 of the nosepiece as polymer flows from the pump 52 through the diebody 61, the meltblowing die insert 96 discharging as filaments throughorifices 116 of the die tip.

The spunbond die insert 97, shown in FIG. 6, comprises a support member126 which may be substantially identical to support member 98 describedpreviously except no air passages are formed therein. The support member126, however, does have the top surface 127, side surfaces 128, andV-shaped grooves 129 which may be identical surfaces 101, 102, andgrooves 104, respectively of the meltblowing die insert 96. Supportmember 126 is provided with a polymer opening or channel 131 whichaligns with channel 72 of the die body 61 with the die insert 97 mountedin cavity 62. Note that since there are no air passages in supportmember 126, the air passages 92 in the die body 61 are blocked off bysurface 127.

The support member 126 is attached to spunbond spinneret 132 whichcomprises a body member 133 and a spinneret plate 134 bolted together bya plurality of bolts 135. The body member 133 in combination with theplate 134 defines a feed chamber 136 having an inlet in registry withpassage 131 of the support member 128. The spinneret plate 134 includesa plurality of flow passages 137 formed therein which reduce down toorifices 138 at their outlets. The orifices 138 may be in accordancewith well-known spunbond practices. (See for example U.S. Pat. Nos.4,340,563; 5,028,375 and 5,545,371).

Each of the die inserts 96 and 97 are selectively inserted into thecavity 62 of the die body 61 and maintained there in place by a pair ofsquare bars 141 which fit into square holes defined by V-grooves 66 and104 or 129 on each side wall of the cavity 62. With the selected dieinsert 96 or 97 in place and the bars 141 inserted, bolts 142 spacedalong, and threaded thereto, each side of die body 61 engages one sideof the bar 141 so that turning the bolts in one direction clamps theinsert sealing onto top surface 64.

The above description of the die body 61 and meltblowing or spunbond dieinserts 96 and 97 makes it clear that the system can be readilyconverted from one mode to the other by simply selecting the insert dieand inserting it into the cavity 62. This, of course, requires theadjustment of the moveable support structure 15 to accommodate theoperating mode. The means for inserting the die insert 96 or 97 intocavity 61 may be manual or automatic. Assembly 214 shown in FIG. 2depicts the spunbond mode and assemblies 216A and 240A depict themeltblowing modes, where polymer melt is delivered from the extruder 22through the melt spinning assembly 16 provided with meltblowing dieinsert 96 and discharged as microsized filaments from the row oforifices 116. The filaments are contacted on opposite sides byconverging hot air streams and carried to and deposited on the conveyor36A.

For the spunbond mode of operation (assembly 214), the spunbond dieinsert 97 is inserted in the die body 61. The moveable substructure 15is moved to its upper position. The quench air assembly 26 and filamentdrawing device 27 are positioned in place by moving the carriage to theposition shown in FIG. 2. Air is delivered to the quench ducts 26 and tothe drawing device 27 while filaments 30 extruded through orifices 138descend from the spinning assembly 16 through the quench zone 45 anddrawing zone 46. The filaments 218 leaving the drawing device aredeposited on the conveyor 36.

Fiberizing die assembly 216A is provided with a meltblowing die insert65A. The other components including extruder 22, platform 12, telescopicsupports 11, 13, polymer delivery line 25, piping 18, motor 53 and driveassembly 54, 56, and pump 52 may be same as those described for dieassembly 214.

Fiberizing assembly 240A represents the core forming station 203, wherein the assembly 240A, the melt spinning assembly 16 is provided with ameltblowing die insert 96 and is mounted above the drawing device 27. Asillustrated, the device 27 may be mounted on the platform 28 which maybe mounted on a carriage for removing or inserting the device 27 in theline. Sheet metal may be also used to define housings 38 and 39 throughwhich the meltblown fibers must pass. As the fibers pass through housing38, drawing zone 46 and housing 39, the downwardly converging sheets ofair contact the meltblown filaments imparting drag forces to furtherdrawdown the fibers. The additional drawdown by the use of the filamentdrawing device produces microsized fibers in the range of 0.5 to 5microns, preferably 1 to 2 microns.

Note that in this alternative mode of meltblowing operation, the DCD(die to collector distance) is much larger than the DCD for conventionalmeltblowing as is apparent by comparing assemblies 216A and 240A. Withthe drawing device 27, the DCD ranges from 3 to 8 feet, preferably from3 to 7 feet and most preferably 4 to 6 feet. The assembly 240A isadapted to produce a high loft web (e.g., basis weight between 5 and 500GSM, preferably between 20 and 100 GSM). Additional die assemblies maybe added at each station as desired, and as illustrated in FIG. 1. Thefiberizing die assembly 207 for manufacturing the spunbond top sheet maybe identical to assembly 214 shown in FIG. 2.

Operation

In operation, the top sheet 206 is made at station 201 by continuouslyfiberizing and calendaring a thermoplastic to form a web which isconveyed to the combining station 205. Optional components 252, 254,described in more detail below, may be prepared at stations 256 and 258and attached to web 206 between stations 201 and 205.

Simultaneously, the bottom sheet 238 is made by fiberizing andcalendaring a thermoplastic to form web 226, which is conveyedsuccessively under meltblowing die assemblies 216A and 216B of station202 where additional fiberized layers are superimposed on web 226. Thecomposite exits station 202 through calendar 233 as bottom sheet 238 andis conveyed to the core forming station 203.

In station 203, one or more fiberization die assemblies (e.g., 240A,240B, and 240C) arranged in series continuously deposit one or morelayers or sublayers onto web 238. The nonwoven webs formed in station203 are characterized as high loft absorbent webs.

The webs exit station 203 as composites 250, which for purposes of thepresent invention, comprise a core layer 237 overlying bottom sheet 238,even though each of these components 237 and 238 may consist of one ormore sublayers bonded together by glue, entanglement or other methods.The core layer/bottom sheet composite 250 is combined with top sheet 235in calendar 205 forming the composite 200. The component layers may bebonded together, for example, by adhesives or thermobonding. Asdescribed in more detail below, the width of composite in exitingcalendar may range from just a few inches (e.g., 6″) to several feet.

In a preferred embodiment, schematically depicted in FIG. 7, thecomposite web 200 exiting calendar 205 is several feet wide to allow forslitting the web 200 into a plurality of individual longitudinal strips200A, 200B, 200C, etc., each strip being approximately the width of asingle diaper. The slitting may be carried out by a conventional slitterindicated at 209.

The individual strips (200A, 200B, and 200C) are processed throughconventional facilities which may include one or more of the following:(a) leg cutouts at station 213, (b) frontal tape attachment at station215, fastener attachments at station 219, and cut off at longitudinalintervals at station 221. These steps may be performed by modulessimilar to that used in converters.

As schematically illustrated in FIG. 7, the composite web 200 exitingcalendar 250 at slitter 209 is slit into individual strips 200A, 200B,200C, etc. which are separated using rollers (not shown) and are inparallel and processed through the steps mentioned above.

A significant advantage of separating the composite web 200 into aplurality of strips (200A, 200B, etc.) vis-à-vis the converter approachis that the apparatus for carrying out the present invention can beoperated at only a fraction of the line speed of the converter. Sincethe conventional converter processes only a single series of diapers,economics require faster and faster operation. For example, line speedsof state-of-the-art converters process from 400 to 800 diapers perminute. The apparatus for carrying out the preferred method of thepresent invention which simultaneously produces a number (n) of strips(200A, 200B, etc.) can be operated at a fraction (1/n) of the speed ofconverter and achieve the same diaper output. For example, the number ofstrips (200A, 200B, etc.) shown in FIG. 7 is ten. Therefore, thisequipment can operate at {fraction (1/10)} the speed of a single-lineconverter and achieve the same diaper output rate. Note also that thetotal width of composite 200 is equal to (n)(t) when n is the number ofslits and t is the width of each slit. Preferably n ranges from 2 to 20and t ranges from 2 inches to 20 inches.

The resin used in the spunbond die assembly 207 or 214 can be any of thecommercially available spunbond grades, including a wide range ofthermoplastic such as polyolefins, polyamides, polyesters, PVA, PVC,polyvinyl alcohol, cellulose acetate, elastomers such as Kraton™ G, andthe like. Polypropylene, because of its availability, is the preferredthermoplastic.

The resin used in the meltblowing dies may be any of the commerciallyavailable meltblowing grade thermoplastic resins. These include a widerange of polyolefins such as polylene and ethylene homopolymers andcopolymers and elastomers such as Kraton™G. Specific thermoplasticsinclude ethylene acrylic copolymers, nylon, polyamides, polyesters,polystyrene, poly(methyl) methacrylate, polytrifluoro1 chloroethylene,polyurethanes, polycarbonates, silicone sulfide, and poly(ethyleneterephthalate), and blends of the above. The preferred resin ispolypropylene. The above list is not intended to be limiting, as new andimproved meltblowing thermoplastic resins continue to be developed.

The following are representative parameters of the preferred embodimentof the present invention:

Broad Range Preferred Range Top Sheet Forming Station (201) Die (length)(M) 0.5 to 6 0.5 to 4.6 Orifice Diameter (inches) 0.010 to 0.050 0.01 to0.2 (Typically 0.015) Spacing (orifices/in) 10 to 40 20 to 35 Orificesspacing (in) 0.05 to 0.250 0.1 to 0.125 diameter (in) 0.001 to 0.0400.016 to 0.020 Quench Ducts size height (m) 0.5 to 2 0.8 to 1.2 width(m) 0.5 to 6 0.5 to 4.5 Die to Collector 3 to 40 6 to 30 distance (DCD)(inches) Polymer Melt Temp. (° F.) 325 to 750 375 to 550 Rate(Gr./hole/min) 0.5 to 5 0.3 to 1.2 Quench Air Temp (° C.) 2 to 20 5 to15 Rate (SCFM/in) 1,000 to 20,000 5,000 to 15,000 Drawing Device Temp.Ambient Rate (SCFM/in) 1 to 100 5 to 20 Core Forming Station (203)Meltblowing Dies 1 to 10 2 to 3 Number Orifices diameter (mm) 0.1 to 1.00.3 to 0.4 spacing (mm) 0.05 to 1.0 0.1 to 0.3 DCD (inches) 3 to 20 3 to8 Polymer Melt Temp. (° C.) 175 to 300 200 to 270 Rate (Gr./hole/min)0.1 to 5 0.2 to 1.2 Primary Air Temp. (° C.) 175 to 300 200 to 275 Rate(SCFM/in) 2 to 100 5 to 30 Bottom Sheet Forming Station (202) SpunbondDies* 1 or 2 1 Number Meltblowing Dies Number 0 to 4 1 to 2 Orificediameter (mm) 0.1 to 1.0 0.3 to 0.4 Orifice spacing (mm) 0.05 to 1.0 0.1to 0.3 DCD (inches) 3 to 20 3 to 8 Polymer Temp. (° C.) 175 to 300 200to 270 Rate (Gr/hole/min) 2 to 5 0.3 to 1.2 Primary Air Temp. (° C.) 175to 300 200 to 275 Rate (SCFM/in) 2 to 100 5 to 30 *The length, orifice,quench ducts, collector specification and operating conditions may bethe same as described for station 201.

Absorbent Composite

With reference to FIG. 3, the three-component composite 200 comprisestop sheet 235, bottom sheet 238, core layer 237 including main absorbentlayer 239 and acquisition/distribution layer 241. The properties anddimensions of the preferred component 200 may be as follows:

Type of Avg. Fiber Basic Wt. Web Layers Size (microns) (GSM) Top sheet(235) Preferred: nonwoven 1 12 to 100 4 to 40 Most Preferred: spunbond 112 to 50 4 to 40 Core Layer (237) Layer 239 preferred 1 5 to 100 2 to100 most preferred 1 5 to 50 10 to 50 Layer 241 preferred 1 to 2 2 to 302 to 100 most preferred 1 to 2 1 to 15 10 to 50 Bottom sheet Spunbond 112 to 100 2 to 100 (238) Meltblown 1-2 1 to 15 .5 to 20

The preferred absorbent composite should have a thickness between 10 milto 500 inches, with the percentage proportion of each layer being asfollows: top sheet 235, 1 to 10%; core layer 237, 25 to 75%; and bottomsheet, 1 to 10%. The preferred thickness of the product will be between25 mil and 200 mil; the most preferred is between 25 and 100 mil.

OPTIONAL EQUIPMENT

Most diaper lines include facilities for applying optional diaperfeatures, which include leg elastic, frontal tapes, waistbands, etc.These options can be applied in the conventional manner. FIG. 1schematic illustrates leg applicator 260 as feeding thin elastic legsections for attachment to bottom sheet 238. Waistband applicator 256,delivers waistbands 254 for attachment to the bottom surface of topsheet 206, and applicator 258 delivers leg cuffs (barriers) forattachment to the top surface of top sheet 206. Absorbent enhancingmaterial such as superabsorbents may be added at strategic locationsalong the line.

ALTERNATIVE EMBODIMENT

It has been stated that at least two, and most preferably three, of thestations 201, 202, and 203, are in-line fiberizing stations. FIG. 8illustrates a preferred embodiment comprising two fiberizing stations(e.g., 201 and 203), and a backsheet roll station 202A. The roll 262 maybe any liquid-impervious sheet material but is preferably a plastic filmsuch as polyethylene or polypropylene film.

In the FIG. 8 embodiment, the stations 201 and 203, respectively, formthe top sheet 235 and core layer 237 as described previously and areconveyed to the combining station 205. Simultaneously, the film sheet264 is unwound and delivered to the combining station 205 where allthree layers are laminated together through calendar 205. A nonwovenlayer unwound from station 202A may be combined with sheet 264, ifdesired.

While the present invention has been illustrated by a description ofvarious embodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the Applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. The invention in its broader aspects istherefore not limited to the specific details, representative apparatusand methods as shown and described. This has been a description of thepresent invention, along with the preferred methods of practicing thepresent invention as currently known. However, the invention itselfshould only be defined by the appended claims, wherein I claim:

What is claimed is:
 1. An in-line system for forming a disposablehygienic absorbent product, comprising: (a) a combining station; b) atop sheet forming station having a first spunbond die and a firstcalender downstream of said first spunbond die for forming a top sheetthat is liquid permeable; (c) a first conveyor for delivering the topsheet in-line from said top sheet forming station to said combiningstation; (d) a bottom sheet forming station having a second spunbonddie, and a second calender downstream from said second spunbond die,first and second meltblowing dies downstream from said second calenderfor forming a substantially liquid impermeable bottom sheet comprising aspunbond layer and two meltblown layers; (e) a core forming stationhaving third, fourth and fifth meltblowing dies arranged in series forforming an absorbent core layer comprising three meltblown layers; (f) asecond conveyor for delivering the bottom sheet in-line to said coreforming station where the core layer is formed on the bottom sheet toform a composite comprising the bottom sheet and the core layer; and (g)a third conveyor for delivering the composite from said core formingstation in-line to said combining station for laminating the compositeto the top sheet to form the disposable hygienic absorbent product. 2.The system of claim 1, further comprising a slitting station downstreamfrom said combining station for slitting the disposable hygienicproducts leaving said combining station into longitudinal strips.
 3. Thesystem of claim 2, further comprising a cutting station for receivingthe strips and cutting them at longitudinal intervals into individualdisposable hygienic products.
 4. The system of claim 1, wherein saidbottom sheet forming station further has a third calender downstreamfrom said first and second meltblowing dies.